The plaintiffs claimed that the sites, which allegedly hosted over 93,000 scanned volumes of manga, are successors to Japanese manga piracy website Mangamura, and are thus violating copyrights and earning profit off it.
The Japanese-language manga piracy site Mangamura became inaccessible in April 2018.
Japanese publishers had filed criminal complaints against the website in summer through fall 2017, and Japanese authorities revealed in May 2018 that they were actively investigating Mangamura.
Hoshi no Romi appears to be named after Romi Hoshino, an alleged administrator of Mangamura.